1) Field of the Invention
The field of the present invention relates to a method and system for providing communication services, including a method and system for transmitting digits (such as DTMF tones) over a communication path.
2) Background
Localized telephone switching systems such as private branch exchanges (PBXs) and key type systems have for many years been available to business offices and other establishments as an alternative or adjunct to public telephone service. A PBX or key system allows users connected to the system to place intra-system telephone calls without accessing the public telephone service. Such a system can provide significant economic benefits, particularly if intra-system telephone traffic is heavy.
On the other hand, when callers using a PBX or key system need to place a call to a party not connected to the system, such outside calls must typically be routed through the PBX or key system controller over landlines to the public telephone company. To accommodate such dual functionality (i.e., intra-system call support and outside call support), special-purpose telephones have been developed for connection to a PBX or key system to allow manual routing of telephone calls. For example, deskset telephones can be provided with buttons corresponding to different telephone lines. By depressing the appropriate button, the user selects between certain designated lines for calls within the system, or different designated lines for calls over the public telephone network.
In other PBX and key systems call routing over the selected lines may be automatic. For example, the user may select an intra-system call or a call over the public telephone network according to the first digit dialed, and the PBX or key system then analyzes the first digit and routes the call to the proper destination using the appropriate vehicle.
While PBX and key systems are useful for providing economical coverage within a private local telephone system, for long distance the PBX users or key system users may still be required to rely on a local exchange carrier (LEC) whose landlines are connected to the PBX. The local exchange carrier then routes the call to along distance carrier. Because the user must pay both the local exchange carrier and long distance carrier for each long distance telephone call, long distance telephone service can be quite costly, particularly if the volume of long distance calls is large.
Besides high costs for long distance service, another potential disadvantage of existing PBX or key telephone systems is that deployment can be difficult or expensive in remote areas. For example, if long distance service or other public network services are required, then deployment of a PBX or key system is generally limited to where landlines have been laid, so that the PBX or key system can have a connection to a local exchange carrier which connects to the long distance provider. If no landlines are present in the desired deployment location, then it can be expensive to connect landlines to provide long distance access for the PBX or key system. Also, conventional PBX or key systems are generally not very mobile where they require an interface with landlines for long distance access or other types of public network services.
There is a need for a communication system having the ability of a PBX or key telephone system to manage local area calls, yet also which can provide access to lower cost, reliable long distance or other network services. There is also a need for a versatile mechanism for allowing PBX or key type systems to achieve relatively inexpensive access to network resources and long distance coverage. There is also a need for a communication system that employs a robust, flexible protocol for providing long distance coverage or other network services to local users of a PBX, key system or other type of local area network.